This invention relates to a seat belt retractor employing dual springs to rewind the seat belt webbing.
The present invention is directed to providing a seat belt system and retractor that will assure sufficient rewind force from two springs to rewind a long length of belt and to overcome other resistances that sometimes result in the belt not being completely rewound when a single spring is used. For the comfort of the wearer, the spring force from the conventional single rewind retractor is kept relatively low, and then additional friction as from a turning loop or from the belt becoming stiffer with age may cause the belt not to be rewound completely. The automobile manufacturers and their customers prefer that the seat belts be fully wound as they exit the vehicle.
There are currently being marketed comfort mechanisms or devices on retractors, which completely block the rewind tension forces of the reel spring from the belt wearer's neck and chest. Such systems are open to the complaint that the wearer may induce too much slack between himself and the belt. Usually, these systems insure that the belt will be completely rewound when the wearer leaves the vehicle by a door plunger which is operated with the wearer's opening of the adjacent door to release the tension-relieving mechanism to assure that the belt will have a chance to rewind onto the retractor reel. Such door plunger and release mechanisms are expensive additions that are desired to be eliminated.
The present invention is directed to a dual spring retractor which eliminates the need for a door-operated plunger to shift from a non-tensioned or reduced-tensioned state and which automatically shifts to have both springs pull on the belt to rewind the same onto the reel.
The present invention provides a retractor in which one or a primary spring is always active to rewind the belt to remove slack in the belt and to eliminate any space between the belt and the wearer's chest. The single spring, of course, applies less tension forces to the wearer's chest and/or neck than does the two springs which are coupled together to rewind the belt. Herein, the two springs pull to rewind the belt whenever the belt is moved at least a predetermined length, for example, six inches. The driver of a vehicle often moves and reaches, e.g., to a glove box or a cigarette lighter, and causes belt extension sufficient to switch from the lighter one spring to the two spring belt force. When the driver returns to his original position, the retractor should either have remained in the single spring mode or be easily reset to its single spring mode to reduce the tensile force being applied to the driver's body. With the present invention, the belt may be extended up to 6 inches from its set position while remaining in its single spring mode.
A number of patents disclose the use of dual spring retractors with one of the springs being disabled to reduce the tension applied to the belt to rewind the belt when the belt is being worn and to have both springs enabled to exert a greater tension force to rewind the belt onto the reel when the wearer no longer is wearing the belt. For instance, U.S. Pat. No. 4,907,757 to Rumpf et al. has both a first wind-up spring and an auxiliary spring in a rotatable member at one end of the shaft. The auxiliary wind-up spring is tightly wound when the belt is rewound on the reel, unwound at belt protraction with the actuating means in position to allow the spindle to rotate relative to the rotatable member, and rewound about the spindle to the taut condition to limit belt retraction relative to the rotatable member. This latter condition provides a predetermined amount of slack in the belt at engagement of the comfort mechanism.
Other dual-spring retractor assemblies utilize a comfort system with worm gear arrangements as noted in U.S. Pat. Nos. 4,664,334 to Asagiri et al. and 4,546,934 to Nishimura et al., which latter arrangement transmits a rotation force of the worm wheel through a clutch to a large spring biasing the reel to retract the belt. The worm is operable after an emergency situation to rewind the large spring to the initial position.
The present application is directed to a less-complex, dual-spring retractor assembly for selectively and easily disengaging one of the rewind springs and to automatically initiate a reduced or tension-eased condition of the rewind force after belt protraction and subsequent retraction. No supplemental or secondary action by the wearer is required to enter the tension-ease mode. A pawl, which is engaged to initiate the tension-eased state at belt protraction beyond the comfort or tension-ease mode, is automatically disengaged at belt protraction to immediately activate the blocked-out spring for returning the assembly to the totally biased condition, that is, both springs acting to rewind the belt. A small subsequent belt retraction, such as one inch, again initiates the tension-ease mode.